- DataInputStream 继承于FilterInputStream ，FilterInputStream继承于InputStream。因此可以说InputSteam是DataInputStream的父类。
- DataInputStream 实现了 DataInput的接口。
重载了以下方法（并设置为final）：
public interface DataInput {
void readFully(byte[] var1) throws IOException;
void readFully(byte[] var1, int var2, int var3) throws IOException;
int skipBytes(int var1) throws IOException;
boolean readBoolean() throws IOException;
byte readByte() throws IOException;
int readUnsignedByte() throws IOException;
short readShort() throws IOException;
int readUnsignedShort() throws IOException;
char readChar() throws IOException;
int readInt() throws IOException;
long readLong() throws IOException;
float readFloat() throws IOException;
double readDouble() throws IOException;
String readLine() throws IOException;
String readUTF() throws IOException;
}
- DataInputStream 重载了FilterInputStream 部分的方法，并设置为final 类型方法，可以继承DataInputStream 类，但是无法重载父类方法。
DataInputStream 方法：
public class DataInputStream extends FilterInputStream implements DataInput {
public DataInputStream(InputStream in) {
super((InputStream)null);
throw new RuntimeException("Stub!");
}
public final int read(byte[] b) throws IOException {
throw new RuntimeException("Stub!");
}
public final int read(byte[] b, int off, int len) throws IOException {
throw new RuntimeException("Stub!");
}
public final void readFully(byte[] b) throws IOException {
throw new RuntimeException("Stub!");
}
public final void readFully(byte[] b, int off, int len) throws IOException {
throw new RuntimeException("Stub!");
}
public final int skipBytes(int n) throws IOException {
throw new RuntimeException("Stub!");
}
public final boolean readBoolean() throws IOException {
throw new RuntimeException("Stub!");
}
public final byte readByte() throws IOException {
throw new RuntimeException("Stub!");
}
public final int readUnsignedByte() throws IOException {
throw new RuntimeException("Stub!");
}
public final short readShort() throws IOException {
throw new RuntimeException("Stub!");
}
public final int readUnsignedShort() throws IOException {
throw new RuntimeException("Stub!");
}
public final char readChar() throws IOException {
throw new RuntimeException("Stub!");
}
public final int readInt() throws IOException {
throw new RuntimeException("Stub!");
}
public final long readLong() throws IOException {
throw new RuntimeException("Stub!");
}
public final float readFloat() throws IOException {
throw new RuntimeException("Stub!");
}
public final double readDouble() throws IOException {
throw new RuntimeException("Stub!");
}
/** @deprecated */
@Deprecated
public final String readLine() throws IOException {
throw new RuntimeException("Stub!");
}
public final String readUTF() throws IOException {
throw new RuntimeException("Stub!");
}
public static final String readUTF(DataInput in) throws IOException {
throw new RuntimeException("Stub!");
}
}
- DataInputStream （数据输入流）允许应用程序以与机器无关方式从底层输入流中读取基本 Java 数据类型。
下面的构造方法用来创建数据输入流对象。
DataInputStream dis = new DataInputStream(InputStream in);
方法描述：
| 序号 | 方法描述 |
|---|---|
| 1 | public final int read(byte[] r, int off, int len)throws IOException 从所包含的输入流中将 len 个字节读入一个字节数组中。如果len为-1，则返回已读字节数。 |
| 2 | Public final int read(byte [] b)throws IOException 从所包含的输入流中读取一定数量的字节，并将它们存储到缓冲区数组 b 中。 |
| 3 | 1. public final Boolean readBooolean()throws IOException, 2. public final byte readByte()throws IOException, 3. public final short readShort()throws IOException 4. public final Int readInt()throws IOException 从输入流中读取字节，返回输入流中两个字节作为对应的基本数据类型返回值。 |
| 4 | public String readLine() throws IOException 从输入流中读取下一文本行。 |
-
实例
下面的例子演示了DataInputStream和DataOutputStream的使用，该例从文本文件test.txt中读取5行，并转换成大写字母，最后保存在另一个文件test1.txt中。
test.tx 文件内容如下：
| runoob1 |
| runoob2 |
| runoob3 |
| runoob4 |
| runoob5 |
代码：
import java.io.*;
public class Test{
public static void main(String args[])throws IOException{
DataInputStream in = new DataInputStream(new FileInputStream("test.txt"));
DataOutputStream out = new DataOutputStream(new FileOutputStream("test1.txt"));
BufferedReader d = new BufferedReader(new InputStreamReader(in));
String count;
while((count = d.readLine()) != null){
String u = count.toUpperCase();
System.out.println(u);
out.writeBytes(u + " ,");
}
d.close();
out.close();
}
}
| 运行结果 |
|---|
| RUNOOB1 |
| RUNOOB2 |
| RUNOOB3 |
| RUNOOB4 |
| RUNOOB5 |
6. 通过实例可以看出流程：
- 创建InputStream对象（所有InputStream的子类对象，可以是文件输入流等）。
- 创建DataInputStream 对象，构造参数为 InputStream 对象
- 创建 InputStreamReader 对象，构造参数为DataInputStream 对象
- 创建 BufferedReader 对象，构造参数为 InputStreamReader 对象
- 最终通过BufferedReader 对象来操作 文件输入流 数据。
